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Special news feature, April 19, 2005

The Hamilton decision

Is he guilty and is the science perfect?

The American Arbitration Association/North American Court of Arbitration
for Sport's decision regarding the Tyler Hamilton blood doping case has set
some interesting precedents and raised some important questions in regard to
sanctioning athletes for drug offences, as Cyclingnews' Chief Online
Editor Jeff Jones reports.

On Monday, April 18, the two out of three AAA/CAS arbitrators ruled that Tyler
Hamilton should be given a two year ban from cycling after testing positive
for a homologous blood transfusion (injecting someone else's blood) at the Vuelta
a España on September 11, 2004. Hamilton also returned an A sample positive
on August 25, 2004, after winning the Olympic Time Trial, but was not sanctioned
for that as his B sample was effectively destroyed by the Athens lab that did
the testing, and no result could be determined from the sample.

Hamilton's Vuelta samples were analysed by the lab in Lausanne, which determined
that both A and B samples showed signs of a mixed red blood cell (RBC) population.
This same lab analysed samples taken from Hamilton's former Phonak teammate
Santiago Perez on October 5, a week after the Vuelta had finished. They too
showed signs of a mixed red blood cell population, and Perez has been given
a two year ban for blood doping by the Spanish Cycling Federation.

Hamilton's defence and USADA's attack

According to the AAA/CAS report, the Respondent, Tyler Hamilton's main points
of defence in his case were:

The test method is insufficiently validated for use in an anti-doping context;

A quantitative as opposed to a visual standard should be used to determine
a 'positive' result;

A 'positive' result means the presence of a mixed red cell population only
and does not prove homologous blood transfusion;

There are other possible explanations for the presence of a mixed red cell
population, such as disease, bone marrow transplantation, intrauterine twin-twin
transfusion, and chimerism.

The claimant, the US Anti-Doping Association (USADA) took the stance that
the arbitration panel had to consider a) Whether Hamilton had mixed populations
for two or more blood cell markers in his Vuelta sample? and b) Whether Hamilton
had given a reasonable explanation of the presence of the mixed RBC population,
other than that of a homologous transfusion.

The test

Hamilton's case was the first time that the homologous blood test (HBTT) developed
by the Australian Ashenden-Nelson group had been used to declare an athlete
in any sport positive. The test was introduced at the Athens Olympics last year
and is based on flow cytometry, which can detect mixed red blood cell populations
by binding surface markers to a fluorescent tag. A histogram of the types of
red blood cells present in a sample can be obtained using a flow cytometer,
and the number of "peaks" seen on the histogram corresponds to the number of
types of red blood cell populations present.

According to criteria set down by the World Anti-Doping Agency (WADA), there
must be "a distinct peak for two different markers on the histograms before
it is concluded that a blood sample contains a mixed population of RBCs." In
normal medicine, only a single peak with a shoulder or tail is necessary to
indicate that there are mixed populations of RBCs. "Therefore, the WADA criterion
gives the benefit of the doubt to the athlete and is a conservative approach
to the assessment of a doping infraction."

In the AAA/CAS report, it is stated that, "There is no division of opinion
or conflicting scientific evidence that indicates any dispute between the various
experts and the published scientific literature that the flow cytometry methodology
can identify a mixed blood cell population. The reliability of the flow cytometer
to identify two blood populations is not challenged in these proceedings."

The test works because although it is quite easy to match blood for a transfusion
for the major surface markers (A, B, O and Rd(D)), it is highly improbable to
match it for all the minor surface markers. The test relies on picking up the
differences, if any, in the minor surface marker profiles. If there are differences,
then the likely, but not the sole, conclusion is that a homologous blood transfusion
has taken place.

In his defence, Hamilton argued that there should be a "lower limit of detection"
for a positive result of 5% of the total RBC in the sample. USADA argued that
the test is merely an identification test. According to the majority of the
scientific literature, the flow cytometer can pick up mixed RBC populations
to a level of 0.07%. According to the Nelson-Ashenden group that developed the
test, "a mixed population of 1.5% - 2.9% is clearly distinguishable from a person's
endogenous RBCs." Furthermore, the Nelson-Ashenden group observed a blood sample
with a mixed population of 0.4%, which was made 111 days after the sample was
drawn.

"Therefore, at any percentage level above 'noise' the test is identifying
two populations or a homogenous population...The noise level of the flow cytometer
used in conducting the HBTT has been calculated at 0.1%, a value that is well
below the 5% threshold argued by the Respondent." Hamilton's histogram showed
a threshold percentage of at least 1.3%, which was deemed sufficient to declare
him positive.

No false positives

One of the most surprising statements in the AAA/CAS report, and one that
was argued against by the dissenting arbitrator Chris Campbell, was that "There
can be no risk of a false positive" in this test. "In fact, in the 48 subjects
reported in the literature, there was 100% accuracy. There is no risk of a false
positive and no need to do so called validation studies."

Do we have an example of the first unfalsifiable scientific method? "There
was no need to do the validation studies" is a different statement to "validation
studies were carried out and there were no false positives reported." It implies
the test is perfect and cannot be questioned. Has science really come this far?
Can we therefore ask WADA to approve Cold Fusion?

The test developers argued, "The markers on the RBCs of a person are the results
of predetermined human genetics. The test identifies two different human blood
populations based on this genetic certainty...If the HBTT identifies two different
RBC populations, it stands to reason that one of the RBC populations must have
come from another person who has his or her own unique, genetically pre-determined
set of RBC surface markers."

This was enough to convince the majority (2 out of 3) of the arbitration panel
that the test was valid.

Of vanishing twins and chimeras

Working under the assumption that Hamilton did in fact have a mixed RBC population
in his body on September 11, 2004, the next part of his defence focused on other
causes of said population. Both disease and bone marrow transplant were "ruled
out as having a zero probability", leaving Hamilton to argue that he had a 'vanishing
twin', that transferred some of its RBCs to Hamilton while he was in the womb,
but disappeared in the first trimester of pregnancy; or that he is a human chimera,
with a natural mixed RBC population.

The evidence states that some of Hamilton's flow cytometry histograms only
show the presence of one type of RBC: one on February 5, 2005, and one taken
by Dr David Housman, a genetics expert and MIT professor, which was not produced
at the hearing but was claimed to show only one peak.

According to testimony given by Australian scientist Dr. Ross Brown, "It is
highly unlikely that 34 years later [after being born], Tyler Hamilton would
have mixed RBC populations indicated on some histograms including the one in
question, and have other histograms with no mixed population indicated. Therefore,
the vanishing twin phenomena can be ruled out as being extremely remote and
not to have been the likely cause of the mixed RBC population."

Hamilton's other argument was that he could be a human chimera, with two different,
genetically distinct RBC populations. Hamilton cited a paper by Van Dijk ("Blood
Group Chimerism in Human Multiple Births", 61 American Journal of Medical Genetics
264 (1996)) that suggested chimerism can occur in up to 30% of the population.
USADA and its experts argued that chimerism is too remote to be taken account
of as the cause.

Hamilton's defence relied heavily on the Van Dijk paper, which "seems to be
an isolated paper in the medical literature." Furthermore, Dr. Ross Brown said
that the figures in the study were "just basically all so wrong, and there's
so many mistakes in the paper that we basically discounted it." Dr Brown added
that he had never observed a chimera in testing over 20,000 blood samples, and
the Red Cross had only observed one chimera case in test millions of blood samples
tested over 20 years.

Other papers suggest that there are no more than 100 cases of human chimerism
in existence, making the probability that Hamilton is a chimera very small.
Then there is the question of Hamilton's differing histograms, some of which
show two peaks, and some of which only show one. Hamilton again relied on the
Van Dijk paper to argue that a human chimera could show a mixed RBC population
on one day and a single population on another. "The Van Dijk research is the
only scientific study of its kind relied on by the Respondent to suggest that
such fluctuations are possible in human chimeras. This assertion loses considerable
strength when it is accepted that human chimerism is an extremely rare occurrence."

Similarly, a theory that Hamilton could be a microchimera, with some of his
mother's RBCs present in his body, was dismissed on the basis that it could
only be detected at a level that was too low to be responsible for the Vuelta
results.

The verdict

The majority of the AAA/CAS panel came to the conclusion that "the mixed RBC
population arising from the Vuelta sample analysis has a very high probability
of having [been] caused by a blood transfusion, and an extremely low to the
point of negligible probability of having been cause by Tyler Hamilton being
a human chimera.

"The Panel therefore finds that a doping violation has been committed by Tyler
Hamilton. the minimum suspension for a first offender in accordance with UCI
Anti-Doping rule 261 is two years. Tyler Hamilton is therefore suspended from
competition for a period of two years commencing, April 18, 2005. All of his
competitive results from September 11, 2004, including the Vuelta competition
are cancelled."

The fall out

It is noteworthy that two out of the three arbitrators agreed on the decision
to declare Hamilton guilty. The third, Christopher L. Campbell, dissented on
several grounds. The first, alluded to above, is that the "Lausanne Laboratory's
failure to provide the measure of uncertainty means its testing method failed
to meet the prevailing standards of the scientific community."

Campbell strongly asserted that "The Testing Method should have accurately
calculated the rate of false positives when the presence of a second RBC population
was not caused by a homologous blood transfusion." Neither the Nelson Study
nor the Lausanne laboratory did this. "False positive results do not appear
to be a problem," said the Nelson Study, which subsequently contradicted itself
and admitted that a second RBC population could be present without a homologous
blood transfusion, i.e. in the case of disease, a bone marrow transplant, a
vanishing twin, or a chimera. Although none of these were deemed likely in Hamilton's
case, it does not clear the test of all doubt.

The Nelson Study did not mention that false positives could also occur if
a lab had not carried out the testing method properly. "This omission is odd
because it was a Nelson validation study that demonstrated that in its quantitative
testing method, laboratories falsely identified second RBC populations where
none were present up to a level of 1.1%. The Nelson Study called these false
positives background events and stated they were caused by incorrect gating
and other problems. Mr Hamilton's sample in this case was within the range of
a background event."

Campbell also criticised the test for being subjective. "If a test was gated
in the wrong region, it would also impact a peak. This also refutes any argument
that if a second peak is visible, the only explanation is a second RBC population."

Campbell raised the issue that the test would be used on women, who could
have fetal cells circulating in their blood system in case of a failed conception.
"Pregnancy in and of itself may establish a long-term, low grade chimeric state
in the human female."

"Because the WADA Transfusion Positivity Criteria and the Testing Methods
fail to provide an accurately calculated rate of false positives, it fails to
satisfy the prevailing standards of the scientific community. In this situation,
USADA should not be able to sustain its initial burden of proof and the case
against Mr. Hamilton should be dismissed," Campbell stated.

He also went into detail about the subjectiveness of the identification method.
When Hamilton's A sample in Athens was first analysed by the laboratory in Greece,
it was deemed negative. "Nevertheless, on September 16, 2004, almost a month
later, the IOC formed an external expert group that ruled Mr. Hamilton's Athens
sample was positive. This group of experts apparently consisted of individuals
paid for developing the Testing Method and individuals who knew the sample belonged
to Mr. Hamilton. Two of the cardinal rules of drug testing are that the individual
doing the analysis (1) should not have a vested interest in the outcome and
(2) should not know the identity of the individual providing the sample."

The visual identification method, "has not been peer reviewed or properly
validated," wrote Campbell. "The panel's acceptance of the deficiencies in the
WADA Criteria and Testing Method establishes a dreadful precedent."

Finally, Campbell referred to Haven Hamilton's response when asked whether
the statements made in the press by high ranking WADA and IOC officials gave
her concerns regarding whether her husband would receive a fair hearing. "Absolutely.
Absolutely. And I think that especially when Jacques Rogge, the president of
the IOC, came out two days before Christmas and said Tyler Hamilton's entire
career should be called into question because of this test result. That's an
unbelievably horrible thing to say about someone...I just think it's inappropriate,
and I don't think any athletes should be subjected to any of that, because it
can't help but influence people."

Campbell concluded by saying, "Athletes should not have to worry that high
ranking officials are sending clear messages to the arbitrators to find the
athlete guilty regardless of the facts of the case. The IOC and WADA should
consider making rules prohibiting such conduct to comply with a very important
fundamental principle of the Olympic movement, fairness."

Hamilton's next step: Appeal to the CAS

In light of the above, it appears that Tyler Hamilton does have a chance to
successfully appeal the AAA/CAS decision to the International Court of Arbitration
for Sport in Lausanne, Switzerland. Although his vanishing twin and chimera
defence is clearly weak, the arguments put forward by Chris Campbell indicate
that the test itself could be challenged for not being properly validated in
either providing a false positive rate or for ensuring that the visual identification
method was not subject to human error.

In Monday's San Jose Mercury News, Hamilton's lawyer Howard Jacobs
was quoted as saying that they do plan to appeal to CAS. "I don't think it is
futile," he said of the 2-1 decision. "It obviously wasn't a slam dunk for USADA."